Method of making glass filaments



Feb. 11, 1958 A. SILVERMAN 2,822,579

METHOD OF MAKING GLASS FILAMENTS Filed March 30, 1953 2 Sheets-Sheet 1 .pm gr I INVEN 1'02 1 0 3 AL EXHNDER 51L VHF/WIN g 7 I A T TORNE).

Feb. 11, 1958 A. SILVERMAN METHOD OF MAKING GLASS FILAMENTS 2 Sheets-Sheet 2 Filed March 3Q, 1953 x QM w .mM K 0 NM T EV T W2. 15 2 .M 2 W m 5 n United States Application March 30, 1953, Serial No. 345,475 2 Claims. (Cl. 1847.3)

This application is a continuation-in-part of application Serial No. 268,871, filed January 29, 1952, now aban' doned.

In the aforementioned application I have described a method of forming glass shapes, such as rods or fibers, by molding a rod composed of bonded discrete particles either of glass-forming oxides, which on fusion produce the glass, or particles of the glass itself. Suitable binders may be used. This material may be extruded to form rods and the rods sintered or otherwise hardened. The rods are passed into a heating zone where they are melted to form a homogeneous melt of the glass. This molten filament of the glass may then be drawn into a thread or blasted into threads.

Where the filaments are formed by a blasting operation, it is desirable that the individual particles, particularly if the glass is a multi-component glass, i. e., a fusion of a plurality of oxides or salts, forming the rod all have the same chemical composition. By using such particles I avoid the danger of segregation of the glass mixture into phases of different melting points prior to total fusion of the shaped mass. This prevents the segregation of the material into a solid, fused, or partially fused phase. This is particularly important where the multi-component glass is composed of a plurality of oxides or salts which are capable of forming a plurality of compounds or complexes of diverse melting points. By employing particles all of which have the same chemical composition, I avoid the above deleterious elfects of phase separation.

In forming glass fibers or filaments from the molten rod, as described above and in my co-pending application Serial No. 268,871, especially when the method of forming the fibers is by blasting the molten strand with a blast of hot gases, it is desirable to employ, in forming the molten rod, particles of preformed glassy material. This is true whether employing a glass formed of a single glass-. forming oxide or salt or a multi-component glass formed of a plurality of glass-forming oxides or salts.

It is thus an object of my invention to form glass filaments from a molded rod composed of individual particles each of which has the same chemical composition.

It is a further object of my invention to form glass particles by fusing the chemical components of the glass into a melt and form small glass particles therefrom, mold the glass particles into a rod of sufficient mechanical strength to be passed into a heating zone and to melt the rod, and form fibers from the molten rod.

These and other objects of my invention will be fur-- ther'described in connection with the drawings, in which Fig. 1 is a schematic flow sheet of one form of my process; and

Fig. 2 is a schematic flow sheet of another form of my process.

Material in hopper 1 is passed via valves 2 and conveyers 3 into mixer 4 and extruder 5. The extruded rod, which may range from A to A of an inch in diameter, is passed by feeder rolls 6 which grip the rod and up rotation advance the extru d rod into the furnace 7.;

atent C ice The furnace 7 is heated by burners 8. The products of combustion exit through 9. Suitable suction may be created in furnace 7 by means of a hot gas blower 10 to prevent hot gas from escaping through the opening 11 through which the rod enters. In passing through the furnace 7, the rod is heated to a temperature of about 500 to 1700 F. whereby it is cured, sintered, and hard ened. The rolls 6 are rotated, one clockwise and the other counter-clockwise, by suitable drive mechanism not shown. H

Rolls 12, driven similarly to rolls 6, move the sintered rod through the opening 14 of the furnace 15. In this furnace, the rod is heated by burners 16 to raise the rod 5 above the melting point of the glass particles sufficiently to give a molten glass of the proper viscosity. The products of combustion exit through 17, pumped,

' if desired, by the hot gas suction fan 18.

The liquid glass 19 is blasted with gas, air, or steam under high pressure, entering through the nozzle 20; alternatively, the nozzle 20 may be a burner and the liquefied glass may be blasted with high velocity, hot combustion gases.

The gases transform the liquid glass into fibers or filaments and also into particles or granules in non-filamentary form. The particles and fibers are carried by the gas stream through the throat 21 of the tunnel 22. The heavier glass particles drop out of the stream into'the hopper 23 while the fibers are carried further into the tunnel until they reach the space 24 where they drop out and are deposited on the foraminous belt 25. The belt 1 is moved in'the direction of the arrows over the suction box 27.

The glass particles and fibers as they enter the tunnel have lost sumcient temperature, due to radiation and convection, to become congealed and then deposit as solid glass particles in the hopper 23 and as solid filaments .on the belt 25. The fibers are deposited asa feltor batt on the belt, and as they exit the tunnel on -;the'bel t they are compacted by a roller 29. A gas outlet 28'and suitable seals at the belt where it exits from the tunnel permit the discharge of gas or steam through the gas outlet 28.

The glass particles in 23 are 'removed'thro ugh'a door 30 and returned by a conveyer 31 either into'4 or into' l, suitable valves 32 and 32' being provided for this purpose. If the particles are too coarse, they may be passed through a grinder 31a before passing into the mixer '4.-

Glass masses ground to a fine powder of 200 mesh or finer contained in 1 are intermixed withfa binder and the mixture extruded. I 8' a Fig. 2 shows an alternative procedure in which the glass particles are made by fragmenting the shaped article, as, for example, by grinding upa rod formed by extruding an intimate mixture. of separate particles of glass-form ing oxides and salts which, when fused together, will form the desired glass The'heterfogeneous mixture of fine particles (200 and finermeshfismixed withabinder and extruded to form a rod. I may use the oxides and: salts referred to above and the binders referred to above.

The intimate mixture is extruded from extruder.105 and passed by rollers 106 through the furnace ,107, f and' heated in the furnace by burners 107 in themanner. similar, and to thetemperatures similar, to that described particles of the material extruded from. These. granules have substantiallyrthe same chemical composi-. tion as the mixture in 105, omitting, however, thewater,

evaporated in 107.

- The crushed granules pass onto sc'reens 111 wher e the 7 particles are separated into particles of various sizes aii 3. pass thi'ough conveyer 112, back to the mixer extruder 105. The coarser granules which have particle sizes greater than those passing from 1 or 31' are passed by the conveyer 114 through the feeder hopper 4-15 con trolled by'ft he rotary valve 1 16=into :thetop of the furnace 117. Hot combustion gases from-burners pass upward through the furnace to discharge {remthe-fiue-1 19. The fines are returned'viaconveyer 130 t'o the original mix passing to the-extruder. yin fallingthro'ugh thefurnace thegranules are preferably-completely 'fused into molten homogeneous-liquidglassdroplets. The gas velocity and temperatureinthe furnace'preferably are-controlled so that such melting is accomplished with sub stantially no-el-utriationthrough 119. .Th'emolten glass droplets drop through the exit throat *IZG'into theblast of gases, steam, or air throughthe n'oz'zle 121 and are converted intosolid filaments-which together with any particles of non-filamentary gas, =are'carried with the stream of gas" into the tunnel 122. As they'enter the tunnel they have dropped in temperature'sothatsolid glass filaments deposit on the belt 123 passing over the suctionbox 124. Thegases exit from 125. Non-filamentary,-solid particles drop out from thegas'stre'a'm into hopper 126*and are screened in screen'12 8. The coarse granules are returned via conveyer 129 to hopper 115 and-arepass'ed-into theshaft furnace 117 while the finerparticles of'si'ze-not suitable for passageto th'e s'haft furnace l fl'are returned to the mixer andextruder via conveyer 130.

Examples of the'glasseswhich may beprocess'ed -accordingto-my invention are given below/not by wayof limitatiombut'as illustrative of my invention. 'In-o'perating the processaccording to the procedures of Fig. 1,

theglasses are *formed in any desired tashion a'nd'the glasses ground to the desired mesh, as described above, and theparticlesn'iixed with the binder and extruded into rodform. "ln operating according-to the-form illustrated 'by'Fig. '2, theglasses are formedby fifsfr'itixing the individual glass' forming oxides-or saltswhich on meltinggive the glassesdesired. Thus, in the following examples where l give the glass formula used in the form illustrated byFigpl, it 'willbe understoodthat theindividual components-of the-glass maybe mixed as discrete particles when using'the procedure of Fig.2, andfvice v'ersa, where I- give the'rnixture in terms of thefindividual oxides or salts components-of the glass, it willbe understood that in operating-according to Fig. '2,"the'se"are niixedas discretepa'rticles of separate cixide "or 'saltingredints. Note, howevenin this casecare 'istobetaken 6f the recirculation "of fused glassparticle's to headmixedwith the glass forinirig ingredien'ts in"thefoi'm of Fig. 2 as well as in the form of Fig.1. Bindersaredescribed foruse in binding the particles and itwill'be finderstdod that they are used in the forms er the invention illustrated by Fig. 1and"Fig. 2.

Various glasses of man different compositions ma be processed I by the procedure illustrated above. Various glass compositions suitable "for use in the above procedure are described in the NordbergPatent No.'2,46 L841 and in the Parker et :11. Patent No. 2,491,761. Other glasses suitable for such use are described in my copending application Se'rial No. 268,871.

I may use calcium alumnae glass wherein CaO and A1 are in 'equimolar quantities or alumino silicate glass containing 2.05 pa'rts' by' weight of A1 0 to one part by weight of SiO I may employ 'calciumsilicate glasses or barium phosphate-barium fluoride glasses, for-example, 10.36 parts'of Ba (PO;) and one part ofiBaF For example, I may inakea mixture of200 parts-by weight of kaolin, '30 parts by weight of A1 0 and-2: parts by weight ofcalcined borax. I may mix therewith 3 parts by weight'of dry wheat paste and 4 parts by weight-of Na SiO The well mixed-mixtureis-mixedwvith water to be-a ipgood I-plastic and extruded. J-The extruded.

rod is heated to a temperature of about 700 C. in furnace 107 and further processed as described. Where I use the glass particles, the glass has the previous cornposition and the glass particles are mixed with the wheat paste and extruded and processed as described.

The above procedure may also be followed using the toll-owing composition: 80par-ts SiO 40 parts CaO, 10 parts MgO, 35 partsboricacidflofl parts kaolin, and 4 parts 'dry' wheat'ipaste, and fiiiiid "with vvat er to a plastic mass. The material is sintered at a temperature of about 700 C. in furna'c'e'107' and processed "as described.

I may alsouse a'mixturemf '501patts'CaSiO arid two parts of dry wheat paste or,-in t he alternative, may use equivalent amounts of CaO a'nd Si0 in place of the calcium silicate. The material mixed with water to a plastic mass is extruded and sintered at a temperature of about 1400? C. to 1700 C. to form the rod and processed as described-above.

ldnay employ a mixture "of '50' partsof talc' and parts of dry wheat paste mixed with water to apla's'ti'c massandextruded and heated in 107toateh1perature of ab 'oiit 1400--C. 'to harden'the rod'andproc'esseda's deserihe'd above v p I "Imay employ- 20:4 parts ofAlgO anazo partsar 'sili'ca andlp'art of calcined borax'and l'f'partof 'drywhe'at paste, heated in 107-to the rod and process the material as described above. v

I-r'istead oE a mixture of glass' formin'g'oxides, "I may employ *a 'singlegl'ass 'formingoxide, for example, 100 pans-cesium and 25 partso'f'flouran'd the mixture'fiiixe'd with water, extruded and heatedin'ltlTto a'temperatnre of-about 1400 C. to harden the rod. I .proc'e's's'the material as described above.

instead of wheat paste or'floury I mayiisean inorganic binder such as V gum'soldby R. T. 'Vanderbelt & CofV gum is a complex *colloidal magnesium alumina silicate having the following composition: SiO 61-11%;Mg0, 13.7%; A1 0 9.3%; CaO, 2.7%; Na' O, 2.9%; H O, 752%. Inemploying this "material I may conveniently use an amount 'suflicient to 'bind' the solid'mixture. -I havefound about 1 to 2%, for example, 1V2% of the Vgu'r'n basedon'the weight of'anh'ydrous solids' used is a useful'percentage. I may thus replace the wheat paste orfiour intheab'ove compositionby V gum as specified b e-t Instead of gum, 'I may, 'whre l employ any materialh'aving an A1 03 co'ntengemploy as a binder ortho' phosphoric acid, or its salts; forexample, calcium orthophiosphate'asa binder. v -Tht 1s,'=r"araynse-2oopans orraonn; 5 parts of calcined'bbrax, a nd"5 mar 85% phosphoric acid mixed with water 'slitficientto'form'aigoodplastic mass, and

. tempeiatiiresiifiicient to convert them to liquid .-.glass process thekanie as described above.

WhiieI have "described particular embodiments it of my invention fdr' purposes of illustration, it' shouldbe underspartan various modifications and adaptationsthereof ma as made within ine spirit of the inven tionas' set forth in"theappendd 'clainis.

A method "offofminggfglass filaments I which compr ses f forniiri'g a mixt'ure Iof particles of glass-forming material,extrudiiig"theresultant mixture into a coherent shapefhea'tingsa'id shape to a; temperaturesufficientito cure and harden said.shape brealgingsaid hardened shape into ffag'rhentsdf'a sizefg reaterithan the particle size of said.glass foimifig'niaterial, heating said fragments to a droplets, and attenuating said -liquid :glass droplets' to form glass filaments.

.;2. methodof formingzglassi filaments whi'ehwemprises forming a:- mixture of par ticles of glassforming material; extruding the resultant mixture 'to fdr'rn aj heating said rodito a 'teniperatnie iiffioient' tweufe and a size greater than the particle size of said glass-forming 2,313,296 Lamesch Mar. 9, 1943 material, heating said fragments to a temperature sufi- 2,369,605 Powell Feb. 13, 1945 cient to convert said fragments to liquid glass droplets, 2,403,740 Muench July 9, 1946 and blasting said droplets with a stream of high velocity 2,450,363 Slayter et a1. Sept. 28, 1948 gas to form glass filaments. 5 2,566,252 Tooley et a1 Aug. 28, 1951 2,585,496 Powell Feb. 12, 1952 References Cited in the file of this patent 2,594,799 Pow ll A 29, .1952

UNITED STATES PATENTS 1,874,799 Peiler Aug. 30, 1932 FOREIGN PATENTS 78 092 Pearce Mar. 31, 19 10 Great Britain Oct. 21, 

1. A METHOD OF FORMING GLASS FILAMENTS WHICH COMPRISES FORMING A MIXTURE OF PARTICLES OF GLASS-FORMING MATERIALS, EXTRUDING THE RESULTANT MIXTURE INTO A COHERENT SHAPE, HEATING SAID SHAPE TO A TEMPERATURE SUFFICIENT TO CURE AND HARDEN SAID SHAPE, BFREAKING HARDENED SHAPE INTO FRAGMENTS OF A SIZE GREATER THAN THE PARTICLE SIZE OF 